I keep my snake room in the low 80s with a thermostat and a space heater.
My colubrids are kept at room temps (low 80s) with no additional heat sources.
My BPs all have a hot end with ambient temps that are the same as the cool end.
My yearling to adult BPs have a hot end of 89-90 provided by flexwatt and an additional thermostat. A few of my bigger snakes have heat pads (exo terra) instead of heat tape (third thermostats). While my hatchlings have a hot end of 86-87 (fourth thermostat).
I would never put a bulb on a snake.
Too many thermostats I think?
Bruce